Question about 2001 Jeep Wrangler

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2001 Jeep wrangler not charging. Alternator has been checked and tests good. Check gauge light on. Alternator not charging power to the field wire from the battery and power to the back alternator on one of the two wires.

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  • mliess Apr 14, 2009

    The fuses have all been checked. I was told the ecm controls the charging of the alternator. The alternator test good.



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On the field wires ones a posative and one a negative and the single post gets connected to a wire that runs straight to the main fuse box in the engine compartment then is fused to another wire that goes to the battery have that fuse checked it could be your problem as far as the feild wires the positive side only works when you start the vehicle up to engage the field

Posted on Apr 13, 2009


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1993 Jeep Wrangler charging problem

nothing wrong with the ECM unless it has the voltage regulator as part of the system
indicates faulty wiring and faulty alternator
have a load test done on the battery
have an auto electrician do a full charging system check
charging voltage should be 14.5-14.8 volts DC
battery voltage should be 12-13.5 volts dropping to 11 volts when cranking the engine
make sure that the drive belt tension is correct and the belt is in good condition

Dec 22, 2017 | 1993 Jeep Wrangler

1 Answer

Loss of power

stock car YJ ? , or all hacked up. (old cars get hacked)
2.5 or 4.0 liter engine? still have a real jeep alternator not upgraded?

loss of electrical power (first rule, we never need to guess.!!!)
not with a voltmeter. (tool that costs $20 )
alternator good (by what means, autozoned?) ( we can find out one car)
but low on gauge. what gauge in dash voltmeter.? sure...
i think you car has no charge lamp only the dash VM.

own an volt meter? a DMM? hand volt meter?

1: if the alternator charge lamp is stuck on driving.
2: is battery voltage at 13.3 to 15vdc with engine at 800 RPM idling
alternator belt not slipping, for sure.....???
if the battery voltage is near 12.5v and falling running that is
an Alternator system failure, note i said, system. !!!

this is first. if we get to here. we can find the real cause.
test 3:
is the charge lamp on keyon, and goes out running?
make sure the big fuse for the alternator in the engine bay fuse
box is not blown, 50amp?

I have no 95 FSM and my online source sucks for 95

Alternator dead: (alt good)
1: belt slipping . engine at 300rpm, nah.
2: fuse blown, the big one. (engine bay fuse box)
3: ;wrong alternator, there are many, most others will fail, even good ones.......
4: alternator ground bad. (end to end, to battery minus)
5: bad wiring to same. bad connections, any to battery or alt.
6: some jeeps the PCM has the field regulator, see link below.
ECU pin 20 , is field pin, it is on 95, 4.0L (engine not stated)

is the CEL lamp on, and throwing code 41 DTC?, alt, field errors?

the alt has 4 pins, battery, field,ground and voltage sense.
The reg is in the PCM. and if bad is a bad $3 transistor..
see same form for fix for that issue..

i think this is same as your. 1996 is big change year.

you can test the alt, PCM wire pulled !, by full fielding the alt.
grounding the field term, no wires on field pin of alt.
see FSM for details on that.
The PCM modulates the field pin to control charge at all times.

Dec 17, 2013 | 1995 Jeep Wrangler

1 Answer

Computer issues on a 99 wrangler

Sounds like voltage regulator in the alternator, have auto-zone do a charging check, may need new alternator.

Mar 01, 2013 | 1999 Jeep Wrangler

2 Answers

I have had the battery & the alternator "shop-tested" (twice) now & they are both "good". My Jeep will run fine for a few miles/ minutes untill "out of the blue" my voltage gauge drops down to...

Your alternator is regulated by the PCM. It could be the PCM or the ignition switch. Might want to try swapping out the shutdown relay just for grins before getting into the ignition switch. Good luck.


Oct 02, 2010 | 1997 Jeep Wrangler

1 Answer

What is the expected output of a alternator in a Jeep 4.0L Sahara (yr. 2000)? My Jeep's ''check gauges'' light came on, and the battery gauge dropped to nothing. Checked the alternator (with a voltage...

You shoulld expect more than 12.8 volts from the alternator up to nearly 14 volts when charging a low battery. The battery can only show the amount of voltage your alternator is sending to it after being used for a while. I would suggest that you have the battery tested & recharged completely, your voltage will be above 12 volts and if it returns to below that , you will know your alternator is not charging. Also, if you test the output of the alternator and see it is below 12 volts after the battery is fully charged at 12+ volts you will have confimed the problem also.

good luck.

Jan 31, 2010 | 2000 Jeep Wrangler

1 Answer

Have a 98 jeep wrangeler 4.0 need to know how to test it I took it in to machine shop they said it was ok but when I put it back on theres no voltage

Pin #20 (dark green wire) on the computer should run to the alternator field circuit. (be aware...Jeep changes color codes more than I change my socks)
The regulator is part of the computer and is not separately available. When the computer sees low voltage it provides a ground to the dark green wire that causes the alternator to begin charging.
To determine if the alternator/regulator combination is working, put a volt meter across the battery terminals (you need a fully charged and load tested battery to do this) With the engine running and no accessories on, the charge rate should be about 13.5 to 13.9 Not above 14. With all accessories on and headlights on high beam, the charge rate should not drop below 13 (at worst 12.5) and should not ever drop below that regardless of how long it runs.
If it does, and the alternator was already proven as good, then the regulator (in your case, the computer) needs to be replaced.
But, before doing that, check the fuses in the power distribution center to make sure the one for the alternator is not blown. Also make sure that the larger alternator wire has full battery voltage (check at the alternator connection) If there is lower or no voltage there, find out why.
Another thing to check is that all ground connections are good at the battery, engine, firewall and especially at the left fender where the computer is connected. (if the ground wires at the computer are not properly grounded it can't send a ground to the alternator
There is a "work around" where you can wire in an old style regulator but I don't remember exactly what goes where but it will turn the check engine light on and therefore may cause you to fail a vehicle inspection though the charging system has nothing to do with emissions..Therefore, I don't recommend it unless you only use the jeep off road.
Hope this helps a bit.

Jan 30, 2010 | 1998 Jeep Wrangler

2 Answers

99 jeep cherokee sport 4.0l 6cyl voltage will go to 19v

The problem sounds intermittent, if you put volt meter on the battery while it is at that 19volt mark/reading(on the gauge cluster) you will be able to see if it is true. If your alternator is really charging over 16volts the lights should be getting brighter then usual and/or they are burning out. Find out ASAP, if the alternator has a defective voltage regulator, it needs to be replaced. Prolong use will damage components.

Jun 18, 2009 | 1999 Jeep Cherokee

1 Answer

1995 Jeep wrangler not charging properly

lf you have replacement cable ends on your battery, check that wires are not corroded under the straps. Also check alternator ground (run a ground wire directly to the alt case) I have seen "lazy" regulators at times but this is very rare. Also make sure drivebelt is tight enough to prevent slipping. Has your battery been charged and load tested?

Mar 28, 2009 | 1995 Jeep Wrangler

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